This invention relates to a power converter, power generating apparatus and plug for connecting a power supply such as a solar battery, wind power generator or fuel cell to a load or commercial power.
Global warming, depletion of fossil fuels, nuclear accidents and radioactive contamination caused by radioactive waste have become problems in recent years, and interest in the global environment and energy resources growing rapidly. Under these circumstances, it is hoped that solar batteries and the like will serve as an inexhaustible and clean energy source and that fuel cells will serve as a power generating devices that produce little or no emissions of carbon dioxide.
System configurations for utilizing solar batteries vary in scale, from several watts to several thousand kilowatts. Such systems are of diverse types. For example, there are systems that utilize power directly, systems that store up power in batteries and systems in which the solar battery is utilized in cooperation with a commercial power source. Solar batteries that can be installed on the roof of one""s home have been introduced and are becoming increasingly popular.
Consideration has also been given to a system configuration in which a small-size power generating apparatus referred to as an MIC (Module Integrated Converter), which converts DC power from a solar battery to AC power, is mounted for each solar battery module and a plug for extracting the alternating current is connected directly to a domestic outlet. A system of this kind is such that electrical connection work and installation work can be performed simply. It is also hoped that mass production of the power generating apparatus will lower cost.
A domestic outlet usually is provided in order to use a load. From the standpoint of preventing electrical shock, the specifications of Japanese Patent Application Laid-Open Nos. 7-282887 and 9-283205 propose a device so adapted that a user will not receive an electrical shock when the user touches a terminal of a partially pulled-out plug. However, conventional domestic outlets and plugs are not fabricated on the premise that a power generating apparatus will be connected to them.
For example, the conventional power converter is internally provided with stand-alone operation preventing functions of two types, namely passive and active, for when reverse current flows into system power. The stand-alone operation preventing function of the passive type attempts to detect stand-alone operation based upon a change in voltage waveform or phase that occurs when there is transition from cooperative operation to stand-alone operation. On the other hand, the stand-alone operation preventing function of the active type detects stand-alone operation upon providing the power generating apparatus with a fluctuation factor that appears in the output only at the time of stand-alone operation. Stand-alone operation occurs when the AC output plug, which is in use by having been inserted into the outlet, is pulled out of the outlet, as mentioned above. In the case of the active function, therefore, this is detected, operation is stopped automatically and safety is assured.
However, with both the passive and active systems described above, it takes at least 0.5 seconds to detect and halt stand-alone operation. There is also the possibility that a malfunction will occur in the circuit that activates the stand-alone operation preventing function. Furthermore, in the case of a conventional power generating apparatus having a comparatively large capacity, the apparatus has a switch and the circuitry can be interrupted. In the case of a low-capacity power generating apparatus, however, the apparatus is connected to the outlet via a plug and the connection is easier to make because a switch is not provided. Even if a switch is provided, the plug may be pulled out inadvertently without operating the switch. In such case a situation will arise in which voltage is applied to the plug terminals. If the user touches a plug terminal, there is the danger that the user will receive an electrical shock.
In a case where a power generating apparatus, which is equipped with a power converter, and a load are connected to a current collector such as a table tap, the generated power and the power consumed by the load will attain a state of equilibrium even if a plug that has been inserted into the commercial-power side of the current collector is pulled out of the outlet. Hence there is the danger that the function for preventing stand-alone operation of the power generating apparatus will not be activated immediately. In such cases also the active terminal of the ordinary plug will be exposed.
Furthermore, a previously proposed protective cover for plug terminals is structurally weak and may break.
The present invention has been devised in order to solve, individually or collectively, the problems of the prior art described above, and an object thereof is to provide a highly safe power converter, power generating apparatus and plug that can be connected in a simple manner without using a special outlet.
According to the present invention, the foregoing object is attained by providing a plug for supplying power by being connected to an outlet, comprising: at least two electrodes; and an insulating member for covering the electrodes when the outlet and plug are not connected and exposing the electrodes when the outlet and plug are connected.
According to the present invention, the foregoing object is attained by providing a power converter having a plug for supplying power by being connected to an outlet, wherein the plug comprises: at least two electrodes; and an insulating member for covering the electrodes when the outlet and plug are not connected and exposing the electrodes when the outlet and plug are connected.
According to the present invention, the foregoing object is attained by providing a power generating apparatus having a plug for supplying power by being connected to an outlet, wherein the plug comprises: at least two electrodes; and an insulating member for covering the electrodes when the outlet and plug are not connected and exposing the electrodes when the outlet and plug are connected.
According to another aspect of the present invention, the foregoing object is attained by providing a plug for supplying power by being connected to an outlet, comprising: at least two electrodes; and switches corresponding to respective ones of the electrodes; wherein the switches are closed when the electrodes are inserted into the outlet.
According to another aspect of the present invention, the foregoing object is attained by providing a power converter having a plug for supplying power by being connected to an outlet, wherein the plug comprises: at least two electrodes; and switches corresponding to respective ones of the electrodes; wherein the switches are opened when the electrodes are inserted into the outlet.
According to another aspect of the present invention, the foregoing object is attained by providing a power generating apparatus having a plug for supplying power by being connected to a domestic outlet, wherein the plug comprises: at least two electrodes; and switches corresponding respective ones of the electrodes; wherein the switches are opened when the electrodes are inserted into the outlet.
According to yet another aspect of the present invention, the foregoing object is attained by providing a plug for supplying power by being connected to an outlet, comprising: at least two electrodes; and a switch that is opened/closed in dependence upon state of connection between the electrodes and the outlet.
According to yet another aspect of the present invention, the foregoing object is attained by providing a power converter having a plug for supplying power by being connected to an outlet, wherein the plug comprises: at least two electrodes; and a switch that is opened/closed in dependence upon state of connection between the electrodes and the outlet.
According to yet another aspect of the present invention, the foregoing object is attained by providing a power generating apparatus having a plug for supplying power by being connected to an outlet, wherein the plug comprises: at least two electrodes; and a switch that is opened/closed in dependence upon state of connection between the electrodes and the outlet.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.